The present invention relates to aircraft; and more particularly, to an aircraft with improved features for enhanced vertical take-off and landing (VTOL) capabilities and high speed (HS) horizontal flight.
Conventional relatively high speed, winged aircraft require long runways for take-offs and landings. In the civil aviation world, this is a significant disadvantage since the pressure for land conservation becomes more and more intense as the population, especially in city and suburban areas, continues to grow. It is also a disadvantage in the military world, since as is well known it is a very distinct advantage to be able to take-off and land without a runway as close to the combat zone as possible, and to deliver as much of a payload as possible. Also, by removing the need to maintain air bases with runways frees up scarce funds for other projects and military personnel for other duties.
Furthermore in the civil/commercial world, there is a significant disadvantage for runway takeoffs and landings in that the aircraft must line up and wait for longer and longerperiods. As the air traffic increases this wait will become more intolerable. Thus, significant advantages in both the domestic and military air travel can be realized by development and successful deployment of HSVTOL aircraft.
Because of these basic long standing shortcomings of fixed wing aircraft and others, VTOL aircraft are establishing more of a presence in the world market, along with more and more helicopter usage. However, none of these newest entries into the field offer the high speed, range and increased payload capability that is needed to fill both the domestic, as well as the military air needs. The closest conceptual approach to providing the answer to these needs is set forth in my prior U.S. Pat. No. 4,773,618, issued Sep. 27, 1988, and which is the predecessor to the present invention.
As set forth in the ""618 patent, there have been numerous attempts in the past to provide a VTOL capable aircraft with relatively high speed horizontal flight capability, as well as acceptable payload and range. Such approaches run the gamet from aircraft that take-off and land in a vertical attitude and then switch to a horizontal attitude for flight, to an aircraft with separate engines for vertical and horizontal flight. These have not met with success, primarily because of the complexity and high cost. One reasonably successful military aircraft is the British Harrier AV-8A and B. This fixed wing aircraft provides limited length runway take-off and landing capability by direct downward vectoring of the hot exhaust gases of the jet engines. Except for the standard helicopters, the only other production aircraft with some vertical take-off and landing capabilities is the U.S. V-22 tilt-rotor fixed wing aircraft, jointly produced by Bell/Textron and Boeing. The first aircraft has far too limited payload and range and the second aircraft has far too limited speed and range.
A recurring problem that continues to plague the development of a truly successful VTOL, including the two described above, is that, compared to conventional aircraft, more than twice the thrust is required for vertical take-off and landing. This requirement alone prevents the aircraft of this type from being successful since the jet engines have to be substantially twice as large. This factor alone makes the aircraft in a particular payload class prohibitively expensive in terms of initial cost, as well as for everyday operation and maintenance.
As far as is known today, my own HSVTOL design of the ""618 patent basically fills these needs. It also solves the problem of efficient attitude control of the aircraft, during both vertical and horizontal flight. The attitude control does not depend on exhaust jet reaction, but instead utilizes in part modulated control of the fan blades of the annular fan assembly that extends around the periphery of the air craft. This design provides greater stability through gyroscopic control, as well as increased maneuverability, and generally more efficient operation. Also, it has the inherent capability of increasing the speed in horizontal flight, and enlarging the payload. The increased efficiency of operation in either mode of operation is proven. With this basic design, the problem of the concentrated, very high temperature, vertical blast of jet exhaust gases being expelled directly from the jet engines against the ground that tend to cause damage to the aircraft and surrounding personnel, as well as to the landing pad, is eliminated.
From the foregoing background review, it is apparent that the next step to advance this technology should be to build on the HSVTOL design of the ""618 patent. Such a redesign of the aircraft would provide for more efficient utilization of jet engine thrust leading to even better performance, increased payload and extended range. Such improvements would focus on structural changes that would allow use of lighter weight materials, particularly in the area of the fan assembly. Such an advance would be provided in part by a unique system for incorporating highly efficient fan jet engines for propulsion, and handling the hot core gases and the surrounding fan air in a novel manner. The new approach would also lead to less expensive materials to be used in the ducting to deliver the high energy gases to the fan assembly. Other components and structural changes would also add to a better performing and reliable aircraft, such as a redesign of the interface hub between the fuselage and the fan assembly. This need includes a better performing bearing and seal arrangement. Another area of primary advance over my prior design would be in improving aircraft attitude control and maneuverability, while at the same time greatly simplifying the system needed for this purpose.
Accordingly, it is the primary object of the present invention to provide an improvement over my prior vertical take-off and landing aircraft for improved performance, allowing substantially increased payload and extending range, along with additional improvement in the control capabilities, especially during vertical flight, and further improving the high speed horizontal flight operation.
Another object of the present invention is to provide an arrangement that allows use of the lighter weight materials that are important for increasing the performance, most notably in the fan assembly and in the plenum.
It is still another object of the present invention to provide the unique system for incorporating highly efficient fan jet engines coupled with handling the hot core gases and the surrounding fan air so as to give maximum thrust, both vertically and horizontally, and at the same time protecting critical components of the aircraft during operation.
It is still object of the present invention to provide improved aircraft attitude control and maneuverability by incorporation of aero flaps with control surfaces positioned in the down wash of the fan assembly.
Additional objects, advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In order to achieve these objectives and to do so in accordance with the purposes of the present invention, a redesigned aircraft of the HSVTOL category is provided, and particularly the aircraft has features that are an advance over the aircraft of my previous ""618 patent. The advances feature the use of fan jet engine to provide separate hot core gas and fan air to drive the annular fan assembly, and aero flaps with surfaces for attitude control. The new aircraft incorporating these and other features provides more efficient vertical take-off and landing capabilities coupled with its supersonic speed performance in horizontal flight. Furthermore, a key advance is made in terms of increased payload and range. Unlike prior VTOL aircraft of very limited capabilities, the present invention is adaptable in this respect to the increased travel needs of today""s modern aviation world, both in the civil and military arenas. With regard to these basic concepts, the present invention is an extension of the concepts and structures of the aircraft shown in my prior U.S. Pat. No. 4,773,618, and this patent is incorporated herein as a reference in its entirety.
A disk-shaped fuselage preferably supports three fan jet engines; one engine mounted in a pod along the center axis of the aircraft and two side engines submerged within the fuselage. Alternatively, a disk shaped fuselage with two side engines submerged within the fuselage can be used. Around the periphery of the aircraft is the redesigned rotatable fan assembly having an array of fan blades extending at an approximately 57xc2x0 angle when fully opened to operative position, that provides enhanced vertical lift during take-off and landing, Inboard of the fan assembly is a nozzle ring having a plurality of nozzles that are angled downwardly at a lesser angle, approximately 15xc2x0 for the purpose of more efficiently ejecting the exhaust from the fan jet engines. The positioning of the nozzles provides maximum thrust to rotate the fan assembly, and at the same time provide direct jet reaction lift to the aircraft.
The rotational thrust is provided primarily by the action/reaction of the mixed, high energy gases being ejected from the nozzles 20-20n+1. The boundary layer of the jet streams may entrain additional air from the surroundings in the nozzle ring.
The hot exhaust core gases and the fan air are delivered separately to the nozzles through the re-engineered plenum, but may be mixed in the nozzles just before ejection. The circular array of nozzles receives the exhaust from composite duct-in-duct feed ducts connected to each of the jet engines and delivered through the annular composite duct-in-duct plenum. Both the feed ducts and the annular plenum are specifically designed to separate the core gases from the relatively cool fan air for very important purposes. The fan air in an outer duct of the duct-in-duct configuration isolates the hot core gases in the inner duct. This arrangement allows lighter materials to be used and also protects the surrounding aircraft structure and operating components, such as the critical annular bearing and seal combination for the fan assembly.
The fan blades of the fan assembly include a leading section and a center section that make up an airfoil portion, and a stationary trailing flap portion. When the fan blades are pivoted to their up or operative position, the airfoil portion provides maximum lift. In addition to the area of low pressure induced by air flow over the airfoil portion, the under surface of the blades provide for high dynamic pressure and energy down wash to enhance the lift function. To control the lift, the positioning of the fan blades, and thus the lift, can be modulated in response to the aircraft""s onboard CPU controller.
In order to direct the hot core exhaust gases into the feed ducts and annular plenum from the fan jet engine for delivery to the nozzles of the nozzle ring, diverter valves are provided. Also, bypass doors on the engine thrust nozzles, when closed, provide a way to force the fan air into the feed ducts and the plenum. During the transition to horizontal flight, the diverter valves and bypass doors are opened to switch the composite exhaust to provide forward thrust to the aircraft. At the same time, the fan blades of the fan assembly are gradually pivoted to a closed position to provide maximum aerodynamic lift over the aircraft. Because of the separation of the hot core gases from the fan air throughout the system until being partially mixed in the nozzles, only the inner ducting of the feed ducts and plenum must be fabricated of a high heat resistant material, such as Inconel metal. The outer ducts can be fabricated of aluminum, or other lightweight materials, such as carbon composite plastic or fiberglass. Similarly, since the ejected exhaust does not pass through the fan blades as in my previous ""618 design, the material used can also be lightweight and inexpensive, and most notably fiberglass/carbon composite reinforced material works well in this instance also.
An important aspect of the present invention is the provision of aero flaps providing control surfaces positioned in the path of the high energy down wash of the fan assembly during vertical flight and a portion of transition to horizontal flight and also into the free air-stream during horizontal flight. Enhanced attitude control, including control of the pitch, roll and yaw of the aircraft is now possible with a substantial savings also in terms of weight, complexity and expense. There is no longer any need to cyclically operate the eyeball valves in the fan blades, as before, since all that is needed is controlled and coordinated actuation of the aero flaps by the on-board controller. It is contemplated that the: side aero flaps not only provide for attitude control (about the aircraft pitch axis), rat but also serve to provide control for any stray gyroscopic forces that are induced during operation. Rear aero flaps are also positioned in the down wash of the fan assembly (during vertical flight) and assist in providing attitude control about the aircraft roll axis. Both sets of aero flaps are adjustable about dual axes.
The aero flaps are positioned in a straight down position when the controller calls for offering no attitude control input. This is typically used during vertical flight. During high, speed, low drag horizontal flight when lift over the top aerodynamic surface is sufficient and there is no call for maneuvering, the aero flaps are positioned along a line that passes through the aircraft center of gravity. From this position during horizontal flight when maneuvering is desired, the aero flaps are twisted oppositely into the free stream air to create rolling torque for pitch control as required. In vertical flight and when optimum control is needed, the flaps are rotated about their positional axis to a position directly across the down wash. In addition to movement about the positional axis, each flap can be pivoted or twisted about its 90xc2x0 spaced control axis to provide infinite variation in the roll control from side to side, or in a pitching motion fore and aft when the set of rear aero flaps is involved in the control operation. Thus, the flapping about the positional axis and twisting about the control axis of the aero flaps in concert can provide any composite motion required by the controller during vertical or horizontal, or in transitional flight in between.
The interface hub of the fuselage, where the separated hot core gases and fan air are transferred to the nozzle ring, includes a highly efficient peripheral array of air bearings for vertical support of the rotatable fan assembly. An array of rollers are rotatably mounted in the hub on vertical axes spaced around the perimeter of the fuselage and provide horizontal support and stability. Viable alternatives to these bearings include all air bearings, all roller and/or foil bearings. A peripheral brush seal is positioned on the fuselage side of the interface hub to contain the flow of the fan air. Advantageously, the hot core gases remain isolated in the center of the duct-in-duct plenum at this point so that the bearings and seal components are protected.
The onboard CPU controller forms the heart of the aircraft control circuit. Operation is through pilot inputs to the control stick, as well as inputs from attitude transducers on the aircraft. Through the CPU controller, all components are operated in concert with each other to provide the highly efficient vertical take-off/landing mode, as well as the transition to and sustained high speed, horizontal flight mode. Through interaction of the various control elements, the aircraft is made highly efficient in all aspects of its operation.
Still other objects of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.